An operating principle of a power supply system of an existing television (TV) set is as follows: an external power supply directly supplies electricity to a standby power-supply circuit, a remote controller transmits a control signal such as a “Power ON” signal, a “Power OFF” signal or the like to the TV set, and the TV set controls the startup or shutdown of a main power supply according to the control signal. Thus, the standby power-supply circuit is always in an operating state, and an operating power of the standby power-supply circuit in the operating state is generally in the range of 0.1 W to 0.5 W. A long accumulation of the aforementioned power will lead to a tremendous waste of energy.